Definition
A row of flush-mounted lights installed along the centerline of a runway, spaced at regular intervals, used to provide visual guidance during takeoff and landing in low-visibility conditions. The lights are white for most of the runway, transition to alternating red and white as the runway end approaches, and are all red over the final portion before the runway end.
Plain English
A line of small lights set into the surface along the middle of the runway. They help the pilot see and stay on the centerline during takeoff or landing when visibility is poor. The colors change near the end of the runway to warn the pilot how much runway is left.
Context Anchor
Seen on airport diagrams as RCL and used during night operations, low-visibility operations, landing, takeoff, and rollout.
Why Pilots Care
Maintains precise runway alignment and reduces the chance of drifting off the paved surface.
Analogy
It is like reflective lane markers down the middle of a road at night: they give your eyes a clear path to follow when the pavement markings are hard to see.
Intuition Check
Do not confuse runway centerline lighting with the painted runway centerline or the lights along the runway edges. RCL means actual lights placed along the runway’s middle line.
Example Sentence 1
As visibility dropped during the approach, the pilot used the runway centerline lighting to stay aligned with the runway.
Example Sentence 2
Runway centerline lighting guided the aircraft straight ahead during the low-visibility takeoff roll.